<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<p>整数1:<input id="num1" type="text"/></p>
<p>整数2:<input id="num2" type="text"/></p>

<p>
    <input type="button" value="相加" onclick="calc(add)"/>
    <input type="button" value="相减" onclick="calc(sub)"/>
    <input type="button" value="相乘" onclick="calc(mul)"/>
    <input type="button" value="相除" onclick="calc(div)"/>
   </p>
<p><input  id="result" type="text"  readonly/></p>

<script>
    function calc(func){
        var result=document.getElementById('result');
        var num1=parseInt(document.getElementById('num1').value);
        var num2=parseInt(document.getElementById('num2').value);
        if(isNaN(num1)||isNaN(num2)){
            alert('请输入数字');
            return false;
        }
            result.value=func(num1,num2);
    }
    function add(num1,num2){
        return num1+num2;
    }
    function sub(num1,num2){
        return num1-num2;
    }
    function mul(num1,num2){
        return num1*num2;
    }
    function div(num1,num2){
        if(num2==0){
            alert('除数不能为0');
            return '';
        }
        return num1/num2;
    }
</script>
</body>
</html>